Refrigerating apparatus



REFR IGERAT ING APPARATUS Filed Oct. 31, 1934 3 Sheets-Sheet 1 March 16, 931. c. AsnCKE-L mum REFRIGERATING APPARATUS Filed Oct. 31, 1934 3 Sheets-Sheet 2 7 WW I Carl Asfickel ma ma: v

Patented Mar. 16, 1937 atte PATENT OFFICE REFRIGERATING APPARATUS Carl A. Stickel, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application October 31,

3 Claims.

This invention relates to refrigerating apparatus and more particularly to control means therefor.

It has already been proposed to provide a control means for refrigerating systemswherein optional manual selective positions are provided in which at least one of the positions provides a sumciently high temperature to provide defrosting during at least a portion of the refrigerating l cycle while all of the remaining positions provide progressively lower temperatures below freezing wherein no defrosting occurs. With such an arrangement, however, when the manual selector is turned to the defrosting position to provide 1.3 continuous defrosting cycles, the temperature of the evaporatorand the food compartment cooled by the evaporator rises and thefood compartment cannot be kept at a normal temperature in such position.

It is an object of my invention to provide a control means for a refrigerating system having a normal position at which the evaporator is kept at freezing temperatures at all times and another position wherein defrosting cycles are provided but which are controlled in such a manher that substantially the same average coolingefiect is provided by the evaporator so as to maintain the compartment to be cooled at substantially the same temperature as is kept when the manual selector-is in the normal position.

Domestic electric refrigerators now in'general use ordinarily have a manual temperature selector having a series of positions providing progressively decreasing maximum and minimum temperatures of the cooling unit but which maintain the temperature differential between the maximum and minimum temperatures of the cooling unit substantially the same throughout the entire range. However, this differential, while properly suited for operation at a normal average temperature, is too wide to obtain the best and most economical results-when operating in the lower temperature ranges for the reason that in order to maintain a relatively lower average temperature with a comparatively wide differential for such a temperature, in order to balance the portion of the time. the evaporator is at a temperature considerably above the average temperature desired, particularly during the off cycle when approaching the maximum tem perature unit, a very low cut-in temperature is required and the compressor is required to operate an excessive time at relatively 'low back pressures to reach such a low temperature. It is, therefore, another object of my inven- 1934, Serial No. 750,869

tion to provide a control means foran electric refrigerator wherein the differential between the maximum and minimum temperatures of the cooling unit is progressively reduced as the temperature regulator is moved toward lower turn perature positions.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view partly in section, and partly diagrammatic showingv a domestic electric refrigerator and refrigerating system including an enlarged view of one form of my improved control means;

Fig. 2 is a sectional view along of Fig. 1;

Fig. 3 is a sectional view along the line 3-3 of Fig. 1; v

Fig. 4 is a view taken along the lines 4-4 of the lines L -2 Fig. 1 showing the manual temperature selector;

Fig. 5 is a view of a modified form of my control means; and

Fig. 6 is a sectional view taken along the lines 6-6 of Fig. 5.

Fig. '7 is a chart showing the evaporator temperatures during the cycling of the refrigerating system in No. 1 cold control position as well as D-1 and D2 position.

As previously stated, the gist of my invention resides in the pro vision of a temperature regulated control means for a' refrigerating system which is provided with a temperature selector which not only provides an accessible readily controllable range adjustment, but which also at the same time in at least the uppermost positions progressively widens the, differential between the upper and lower temperatures of the cooling unit sufliciently to bringthe upper temperature limit above freezing and to lower the lower temperature limit sufficiently to compensate for the raising of the upper temperature limit so as to provide substantially the same amount of refrigeration and to maintain the compartment to be cooled at substantially the same average temperatures. However, in some cases, it may be found desirable to stop short of this result and to only partially compensate for the increased upper temperature limit by widening the temperature differential only a portion of the amount required to give complete compensation. In one form of my invention, this scheme of changing the differential alongwith carried to an advantage into the lower temperature ranges where the temperature differential is progressively reduced as the temperature selector is moved into -the lower temperature ranges in order to provide more economical operation at the lower temperatures desired.

Referring to the drawings, and more particularly to Fig. 1, there is shown a domestic electric refrigerator 20 having a food compartment 22 containing a, refrigerant evaporator 24 of some suitable type such as the float controlled flooded type which is supplied with liquid refrigerant'by a refrigerant liquefying apparatus, generally designated by the reference character 26 and which comprises a compressor 28 driven by an electric motor 34 for compressing the refrigerant and for forwarding the compressed refrigerant to a condenserwhere the compressed refrigerant is liquefied and collected in a receiver 32. From the receiver 32, the liquid refrigerant is forwarded through a supply conduit 36 to the evaporator 24 which is provided with a float controlled valve for controlling the admission of liquid from the supply conduit 36 into the evapo-" rator. The liquid refrigerant within the evaposide of the casing with a removable manually rator 24 evaporates and absorbs heat from the atmosphere within the compartment 22 and this evaporated refrigerant is returned to the compressor 28 through the return conduit 38.

The operation of the electric motor 34 and the refrigerant liquefying apparatus 26 is controlled by my improved control apparatus 40 in order to maintain the temperature in the evaporator 24 between desired limits in order to cool the food compartment 22 as desired. This control apparatus 40 is provided with a metal bellows 42 connected by the tubing 44 with the-return conduit 38 of the refrigerating system so that it is responsive to the pressure and the temperature of the evaporator 24. This bellows 42 acts upon a main lever 46 pivoted at 41, which lever is connected at its free end to a secondary lever 48 forming a part of the double toggle snap acting mechanism. This secondary lever is connected by a tension toggle spring 50 to the anchor post 52 of a contact carrying lever 54 pivoted upon the pin 56. This lever is provided with a depending portion 58 carrying a contact bar 60 adapted to bridge the contacts 62 located in series with the electric motor circuit 64 of the electric motor 34. The expansion of the bellows 42 and the consequent movement of the main lever 46 is controlled by a compression spring 66 which bears upon the main lever and which is held at its upper end by a nut 68 threaded upon the threaded lower end of the temperature selecting screw 10. This temperature selecting or regulating screw is rotatably mounted in the casing 4| of the control means and is provided on the outer controllable combined temperature selector knob and indicating means 12. The rotation of the selecting knob 12 moves the nut 68 upwardly and downwardly to change the tension of the compression spring 66 so as to change both the opening and closing'temperatures of the switch contacts. The temperature regulating screw 10 is preferably set to the desired normal adjustment after which the knob 12 isattached. The movement of the knob is preferably limited to one turn. This is in reality a convenient form of range adjustment.

There is also provided a diffe t j s position.

shown in Fig. 1 is just at the point of tripping the movement of the temperature selector is also ment in the form of a screw 14, the lower end of which acts as a stop for the upper projecting portion 16 of the contact carrying lever 54. This screw I4 limits the movement of the contact carrying lever 54 away from the closed contact The double toggle mechanism .as

from open position to closed position. This takes place when the. secondary lever 48 and the tension toggle spring 50 are carried across dead center position. The angularity of the main lever 46 and the angularity of the secondary lever 48 and the toggle spring 50 at the time of tripping to closed position depends upon the particular position of the projecting portion 16 which serves as a stop for the secondary lever, as well as engages the lower end of the differential screw 14. Thus, by moving the differential screw 14 upwardly, the upper temperature limit of the evaporator 24 is raised, while lowering the screw, the upper temperature limit is lowered without affecting the lower temperature limit.

This arrangement so far described provides means for setting the temperature differential and provides means whereby a series of different average temperatures of the cooling unit may be maintained at the same differential. It has been found desirable to provide one position of the temperature selector at which both the upper and lower temperature limits of the cooling unit are maintained below freezing and which also provides the proper amount of refrigeration to maintain the temperature within the compartment 22 at a desirable temperature. However, such operation causes the accumulation of frost upon the cooling unit which acts as an insulator and, thereby, reduces the heat transfer between the atmosphere in the compartment 22 and the walls of the evaporator so that an insufiicient amount of refrigeration is supplied to the compartment.

According to my invention, I provide an additional position of the temperature selector whereby the upper temperature limit of the evaporating means is increased to a point above freezing, while the temperature differential is increased and the lower temperature limit is lowered sufiiciently so that the same amount of refrigeration is supplied by the evaporator 24 as in the aforesaid normal position so that the average temperature within the compartment 22 is maintained substantially the same.

In order to do this, I provide a cam upon the threaded temperature regulating screw Hi D2 and an off" position, as well as other positions designated by the numbers 1 to 6 inclusive, which are for progressively lowertemperatures below freezing. Also shown in this figure in dotted lines, is the cam 80 provided with a raised portion 96 which coaots with the follower 82 when the temperature selector is in the D1 position, a higher raised portion 96 which cooperates with the follower when the temperature selector is moved to D2 position, while a third and still higher raised portion I62 is provided which coopao'raese erates with the cam follower 82 when the temper ature selector is moved to off position.

The cam 94 is provided with an arcuate portion I94 as well as raised portions I06 and I08. These cam surfaces act against a follower H6 forming a slidable part of the contact carrying lever 54 and which carries the anchor post 52 of the double toggle snap acting mechanism at its opposite end. This follower III] is slidably mounted in the depending portion 58 of the contact carrying lever 54. When the temperature regulating knob is turned to the D1 position, the follower 82 is moved toward the right as 'viewed in Fig. 1 by the cam surface 56 against the ten- 66 of the cam 94 is turned in a clockwise direction so as to cam the nose of the slidable cam follower I Ill into engagement with the raised portion I06 of the cam 94. This will mov the slidable cam follower I10 and-its ancif; post 52 toward the left thereby further str tching the tension toggle spring 50 and thereby causing the differential of the snap acting mechanism to be widened an equal amount in both directions. Likewise, when the temperature selecting knob is "moved to D2 position, the last raised portion upon the cam 80 aswell as the cam 94 come into engagement with their respective followers and the tension of' thetoggle spring 59 is further increased to furtherwiden the differential of the snap acting mechanism equally in both directions.

However, it is known that because of the fact that it is necessary to operate at low back pressures to obtain low temperatures, and the compressor pumps less and operates longer at low back pressures, the average temperature of the evaporator is less than the mean between the upper and lower temperature limits. For this 40 reason, it is desirable that the upper temperature limit be increased more than'the lower temperature limit is lowered in order to maintainthe average evaporator temperature and the amount of refrigeration supply substantially the same. In this form of my control means, this is taken care of by the fact that in moving the-temperature selector 12 to the defrosting position, the temperature regulating screw is also turned to increase the tension on the spring 66 so that this will tend to raise both the upper and lower temperature limits and this tendency combined with i the changing of the differential in both directions is so proportioned that the upper temperature limit is increased and the lower temperature limit is lowered a sufficient amount to provide substantially the same average temperature of the cooling unit 24. When the temperature selecting knob 12 is turned to the ofi position, the projecting portion II2 on the cam member 94 comes into contact with the protruding end II4 on the contact carrying lever' 54 to forcibly move this lever to open circuit position where the contact bar is separated from the contacts 62 to hold open the electric motor circuit. This, I of course, stops the operationof the system.

In Figs. 5 and 6, another embodiment is shown in which there is similarly provided a bellows I42 within a casing 'I4I which acts upon a main lever I46 pivoted at I41 which is connectedto a secondary lever I48. of a double toggle snap acting mechanism. This secondary lever I48 is connected by a tension toggle spring I56 to the anchor post I52 of a contact carrying lever I54 pivotally mounted upon the pivot pin I56. Thus 75 far, this mechanism is very similar to the first desion of the spring 84 so that the bell crank lever small amount.

scribed embodiment. The contact carrying lever is provided with a contact bar I60 on its lower surface which is adapted to bridge the contacts I62 located in series with the electric motor circuit. The open circuit position of the contact 'end to a lever 2| 0 which is pivoted at 2I2 and which is connected by a pin 2 to a nut 2I6 threaded upon a vertical threaded shaft 2 I 8 which is rotatably mounted within thecase or housing I4I. This nut 2I6 is prevented from rotating with the shaft 2! by a vertical rod 222 located directly behind the shaft 2I8. Fastened to the upper end of this shaft is a temperature selector knob I12 which is removable and which preferably has its rotation limited to one turn. By turning the temperature selector knob I12 and the shaft 2I8, thevlever 2| 9 may be moved upwardly or downwardly to change the tension upon the spring II6 to vary the pressures and temperatures at which the bellows I42 movesthe switch contacts to open and closed position.

According to my invention, I provide means operated by this same temperature regulating shaft to vary the differential of both the circuit opening and circuit closing points throughout the entire range of the temperature selector. This is done by mounting the contacts I62 upon a nut 229 which is threaded upon the shaft 2 I 8 and held from rotation by the rod 222. Likewise, the stop I 14 forms part of a nut 224 which is likewise threaded upon the rod 2 I 8 and held from rotation by the rod 222. The lower end of the rod 2I8 is provided with a left hand thread while the upper portion is provided with a right hand thread; Thus, the two nuts 229 and 224 are either moved closer together or farther apart, depending upon the direction of rotation of the rod 2I8. Inasmuch as the nut 2I6 is also threaded upon the left hand thread when the temperature selector knob is turned toward the right, the nut 224 moves upwardly while the nuts 226 and 2 I6 move downwardly so that'the tension of the spring H6 is increased while the contacts I62 are lowered and the stop I14 is raised. The increasing of the tension of the spring I66 tends to increase both the cut-in and cut-out points, while the upward movement of the stop I14 tends to raise the cut-in point, while the lowering of the contacts I62 tends to lower the cut-out point. By the proportioning of the lead of the threads, and/or the mechanical advantage of the lever 2I0, these characteristics may be varied. If desired, a cam or a multiple leverage mechanism maybe used in place of the simple lever 2I0 to provide a change in the tension of the spring I66 which will be small in the upper ranges and larger in the lower ranges. Thus, if desired, these difierent' settings maybe so changed that at all points throughout the range ofv adjustment, the amount of refrigeration sup- I plied and the average temperature is substantially the same while the differential is changed so that when the differential is very wide, a defrosting temperature is reached before the switch closes. In such a case, the movement of the free end of the lever 2IIl is made comparatively small so that the tension of the spring I66 is changed only. a However, it is more desirable that the control provide a colder average temperature when the differential is small and a warmer temperature when the differential is wide which is sufliciently high to make the cut-in point at a defrosting temperature. In such a case, the movement of the free end of the lever 2l0 is made greater so as to provide a-greater change in the tension of the spring I66. In this way, I am able to provide a control which operates the refrigerating system upon a small differential when a lower average temperature is desired, but which operates upon a wider differential when a higher temperature is desired, particularly for defrosting periods. In this way, a more economical opera tion of a refrigerating system is obtained.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form,

it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Refrigerating apparatus including an insulated compartment to be kept cool and a refrigerant evaporating means in heat exchange relation therewith for cooling the compartment, a

refrigerant liquefying apparatus for supplying liquid refrigerant to the evaporating means and for withdrawing evaporated refrigerant therefrom, control means for controlling the starting and stopping of the liquefying apparatus according to predetermined high and low temperatures of the evaporating means, said control 'means including selective manually operable tion therewith for cooling the compartment, a. refrigerant liquefying apparatus for supplying liquid refrigerant to the evaporating-means and for withdrawing evaporated refrigerant therefrom, control means for starting and stopping of the circulation of refrigerant through the evaporating means according to predetermined high and low temperatures of the evaporating means, said 'control means including selective manually operable means having a plurality of operable positions, said selective means when in one operable position causing the starting and stopping of the circulation of refrigerant through the evaporating means at freezing temperatures of the evaporating means and when in another operable'position simultaneously causing the starting of the circulation of refrigerant at frost melting temperatures of the evaporating means and causing the stopping of the circulation of refrigerant at a lower temperature of the evaporating means to compensate for the higher starting temperature in order to maintain substantially the same cooling effect.

3. Refrigerating apparatus including an insulated compartment to be kept cool and a refrigerant evaporating means in heat exchange relation therewith for cooling the compartment, means for. circulating refrigerant through the evaporating means, control means for controlling the circulation of refrigerant according to predetermined high and low temperatures of the evaporating means, said control means including means for normally causing starting and stopping the circulation of refrigerant at freezing temperatures of the evaporating means, said control means also having selective means for causing the starting of the circulation of refrigerant 'at a temperature above freezing of the evaporating means and for causing the stopping of the circulation of refrigerant at temperatures of the evaporating means below those at which the circulation is normally stopped.

' CARL A. STICKEL. 

